how to remove the wall of illusions in The Witcher 3 (The Witcher 3: Wild Hunt)

button e-but before that you need to go through the plot where you will be taught this)

Keira Metz will give you the Eye of Nehalena

you need a special stone, Keira Metz will give it to you according to the plot, when you look for Ciri in the cave.

It's called looking in a book and seeing a fig